1. Technical Field
The present disclosure relates to systems and methods that compensate for port to port crosstalk noise generated from electrical component proximity within a multiport assembly.
2. Background Art
Unshielded Twisted Pair (UTP) cable is a popular and widely used source of data transfer media because it is a very flexible and low cost media that can be used for either voice or data communications. In fact, UTP cable has rapidly become the de facto standard for Local Area Networks (LANs), in-building voice, and data communications applications. As UTP cabling continues to be an essential choice of media transmission, new and improved methods must be employed to meet the requirements of a transmitting data source. In an UTP, a pair of copper wires generally forms a twisted pair. For example, a pair of copper wires with diameters of 0.4-0.8 mm may be twisted together and wrapped with an insulated coating to form an UTP. The twisting of the wires increases the noise immunity and reduces the bit error rate (BER) of the data transmission to some degree. In addition, using two wires, rather than one, to carry each signal permits differential signaling to be utilized. Differential signaling is generally immune to the effects of external electrical noise.
The wide acceptance of UTP for data and voice transmission is primarily due to the large installed base, low cost, and ease of new installation. Demands have increased on networks using UTP systems, such as 1000 Mbit/s and 10,000 Mbit/s transmission rates, which has forced the development of industry standards requiring higher system bandwidth performance and lower noise-connecting hardware. What began as a need for connecting hardware to provide near-end crosstalk (NEXT) loss of less than −36 dB at 16 MHz, has evolved to −54 dB at 100 MHz and −34 dB at 500 MHz for category 6 and future category 6a systems, respectively. As the transmission rates have increased, so has system noise, in particular NEXT, Far-End Crosstalk (FEXT) and Alien Near-End and Far-End Crosstalk (ANEXT/AFEXT).
For any data transmission event, a received signal will consist of a transmission signal modified by various distortions. The distortions are added by the transmission system, along with additional unwanted signals inserted somewhere between transmission and reception. The unwanted signals are referred to as noise. Noise is a major limiting factor in the performance of today's communication systems. Problems that arise from noise include but are not limited to data errors, system malfunctions, and loss of desired signals.
Generally, crosstalk noise occurs when a signal from one source is coupled to another line. Crosstalk noise is also classified as electromagnetic interference (EMI). EMI occurs through the radiation of electromagnetic energy. Electromagnetic energy waves can be derived using Maxwell's wave equations. These equations are defined using two components: electric and magnetic fields. In unbounded free space, a sinusoidal disturbance propagates as a transverse electromagnetic wave. This means that the electric field vectors are perpendicular to the magnetic field vectors that lie in a plane perpendicular to the direction of the wave. NEXT noise is the effect of near-field capacitive (electrostatic) and inductive (magnetic) coupling between source and victim electrical transmissions. NEXT increases the additive noise at the receiver and therefore degrades the signal-to-noise ratio (SNR).
Crosstalk using a plug that mates to a modular insert setup such as that illustrated in FIG. 1 will increase as system speeds or system transmission frequencies increase. The transposition or twisting of the transmitting wire pair helps minimize crosstalk generated in a cable. However, coupling occurs as the signal travels through untwisted sections, such as plugs and plug contacts.
In a differential balance two wire per pair transmission system, signals that travel along each wire (or other media) are equal in amplitude but opposite in phase. These signals at any instantaneous moment in time couple electric and/or magnetic fields to adjacent lines, which reduces their SNR. The acceptable SNR depends on the type or quality of service that is required by the system. To remove the noise components, a forward signal equal but opposite to the original signal may be induced. According to Fourier's wave theory and Maxwell's theory of electromagnetic fields, by coupling the opposite phase of the transmitted signal to a previously coupled adjacent line signal, the two signals cancel each other completely and therefore remove the noise from the adjacent line.
The American National Standards Institute/Telecommunication Industry Association/Electronics Industries Alliance (ANSI/TIA/EIA) has finalized a standard defining electrical performance for systems that utilize the 1-250 MHz frequency bandwidth range for category 6 electrical performances. The increasing demand for more bandwidth and improved communication systems (e.g., Ethernet 1000BASE-T) on UTP cabling will require improved connecting hardware. The ANSI/TIA/EIA is also working on higher standards defining electrical performance for systems that utilize the 1-500 MHz frequency bandwidth range for 100 meters of UTP cabling transmission called 100 Ohm Augmented Category 6 Cabling. The TIA/EIA 568B.2-10 titled, “Transmission Performance Specification for 4 Pair 100 Ohm Augmented Category 6 Cabling” for channel link defines the specified frequency bandwidth of 1-500 MHz, and a minimum NEXT value of −33.1 dB at 100 MHz and −26 dB at 500 MHz. By increasing the bandwidth from 1-250 MHz (category 6) to 1-500 MHz (Augmented category 6, C6a), tighter controls of component noise susceptibility are necessary. With the development of new standards, new connecting hardware noise levels will have to be lower than that of old connecting hardware used in category 5e and 6 media systems. FCC part 68.500 provides standard mechanical dimensions to ensure compatibility and matability between modular plug housings of different manufacturers.
Attempts to reduce internal crosstalk noise in electrical connectors have been made. For example, U.S. Pat. No. 5,618,185 to Aekins discloses a reduced crosstalk electrical connector including a housing that receives four pairs of elongated contacts for receiving electrical signals and a printed circuit board (PCB). The PCB utilizes a single stage or cancellator section (signal compensation) for reducing NEXT. That stage contains a cancellator that is opposite the original noise magnitude's polarity. NEXT noises are reduced internally, but external noise signals relative to adjacent ports are not reduced.
Additional attempts to reduce internal crosstalk noise in electrical connectors include, for example, U.S. Pat. No. 5,997,358 to Adriaenssens et al., which discloses a reduced crosstalk electrical connector that utilizes two stages of signal compensation for reducing NEXT. The first stage is opposite the original noise polarity and the second stage is of the same polarity as the original noise.
Thus, methods for providing positive compensation to reduce crosstalk noise in connecting hardware are addressed in U.S. Pat. No. 5,618,185 to Aekins and U.S. Pat. No. 5,299,956 to Brownell et al., the contents of which are hereby incorporated by reference. Methods for providing positive and negative compensation to reduce crosstalk noise in connecting hardware is addressed in U.S. Pat. No. 6,840,816 to Aekins and U.S. Pat. No. 5,997,358 to Adriaenssens et al., the contents of which are hereby incorporated by reference.
Although previously disclosed circuitry systems described above have been used to improve and/or compensate for internal crosstalk noise, they do not improve external crosstalk noise, such as ANEXT or AFEXT. ANEXT is the coupled crosstalk noise that occurs from one adjacent signaling media port to another signaling media port at the near-end of transmission. AFEXT is the coupled crosstalk noise that occurs from one adjacent signaling media port to another signaling media port at the far-end (received) transmission. The prior art strictly deals with internal noise issues of a connecting hardware and does not reduce external noise generated by other signal path components.
A need exists for an improved UTP connector that reduces internal as well as external noise, generated by adjacent ports, for all frequencies, e.g., up to and including the category 6a transmission levels. Moreover, a need exists for systems/techniques for rebalancing of noise on a single controlled source that contains non-interchangeable components. A further need exists for an improved connector that does not lessen the impedance characteristics of connected wire pairs and minimizes common mode (CM) noise that occurs from typical cancellator/compensation circuits. These and other needs are addressed by the systems and methods of the present disclosure.